The use of billboards or other large-scale displays is a popular way to convey information to the public, whether as an advertisement or public service message on the side of a highway, as a display printed on a side of a vehicle such as a truck, or as an informational message displayed on the side of a building.
Historically, billboards were simple generally flat surfaces upon which written material was placed, for example, by painting or drawing a message intended for public viewing. Messages printed on large paper sheets were pasted on generally flat surfaces, also known as substrates, and subsequent messages were simply pasted over previous ones. As billboards increased in size it became too difficult to print the message on a single large sheet of paper, and thus multiple sheets were used and assembled by a worker onto the billboard.
In recent years printed vinyl sheets have replaced printed paper sheets as a popular medium for large-scale messaging. Vinyl is stronger than paper, more tear resistant, easier to handle, and typically lasts longer than paper. Paper has to be glued to a substrate and generally lasts approximately thirty days before deterioration is noticeable. In addition, instead of requiring multiple smaller sheets, a message can be printed on one large sheet. In conventional methods of mounting such vinyl billboards, a large sheet is draped over a frame and/or a substrate and the four edges are secured so that the message printed on the sheet is displayed.
For example, one conventional method for securing the sheet to the frame is to drape the vinyl sheet over the frame and tie opposing edges together on the back, using rope or cord tied to itself or tied to braces on the back of a substrate. Another method, disclosed in U.S. Pat. No. 7,168,197 to Siegenthaler, uses a series of adjustable J-shaped hooks mounted on clips fastened to the billboard frame, with the J-shaped hooks passing through holes in the vinyl sheet to secure the sheet to the frame. Still another conventional method uses long rods, known as gripper rods or gripper bars, which are inserted into pockets in the four edges of a vinyl sheet created by folding and heat welding the edges of the sheet. After the rod is inserted into the pockets, the sheet is mounted to the frame. One way of mounting such a vinyl sheet is to use J-shaped hooks mounted around the four edges of the billboard, which, like the J-shaped hooks disclosed in Siegenthaler, pass through holes in the vinyl sheet. Another way of mounting a vinyl sheet having a gripper bar is to use a threaded clip that squeezes the gripper bar between two surfaces of the clip. Yet another way is to use a clip having an H-shaped channel, with a locking pin inserted in the bottom of the “H” after the gripper bar is in place.
However, the holes in the vinyl sheets can reduce the overall strength of the sheet, making it susceptible to tearing and uneven tensioning, which in turn can result in sags, folds, or other distortions of the sheet making the message difficult to read. In addition, light-weight vinyl sheets have become popular, which cost less and are more flexible but are thinner and have less strength than heavier sheets, making them less unsuitable for the heat-welding required for installation of gripper bars and generally more susceptible to tearing from the holes required for use of J-hooks. The subject matter cable tensioning apparatus requires no welding, reinforcement, or other treatment of the edge of the media.